In electrical circuits, more particularly in complex integrated circuits, reference voltage sources are required which deliver a constant output voltage which is independent of the temperature, loading and amplitude of the feed voltage. A known circuit suitable for this purpose is the so-called "Widlar circuit" or band gap reference circuit which is disclosed in the journal of the IEEE, 1970, "International Solid-State Circuits Conference," pp. 158 to 159. Such a circuit has three resistors.
There is also known a modification of the above circuit which comprises only two resistors.
There is also known a further modification of the above circuits from the journal of the IEEE 1980, page 219.
The above-mentioned circuits are described in detail below with reference to FIGS. 1, 2 and 3 respectively of the drawings.